Vibrations from rotating machines or the like cause unwanted noise, undue wear on moving parts, inefficiency, stress and fatigue failures, and can even present a hazard. For example, it is critical that our nation's submarines and torpedoes do not emit vibrations lest they be detected by enemy ships.
Actively damping such vibrations can be effected by a controller apparatus including a wave form generator which provides vibrations having the same frequency and amplitude but of opposed phase to that of the vibrations from the source.
Such devices, however, are fairly complicated: the amplitude, and phase characteristics of the source vibrations at each frequency must be analyzed. This analysis involves solving complicated mathematical expressions. The associated complex electrical circuitry, signal processing, and computer programming make active vibration damping difficult to accomplish in real time.